root
74 lines
2.1 KiB
TypeScript
74 lines
2.1 KiB
TypeScript
import {computed, effect, Signal, signal, WritableSignal} from '@angular/core';
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export class IndexedArray<T> {
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protected list: WritableSignal<T[]> = signal([]);
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protected currentIndex: WritableSignal<number> = signal(0);
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public playlist: Signal<T[]> = this.list.asReadonly();
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public index: Signal<number> = this.currentIndex.asReadonly();
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public current: Signal<T|null>;
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constructor() {
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this.current = computed(() : T | null => {
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if (this.currentIndex() > -1 && this.list().length === 0) return null;
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return this.list()[this.currentIndex()];
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});
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}
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next(): T | null {
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const length = this.list().length;
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if (length === 0) return null;
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if (length === 1) return this.list()[0];
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if (this.currentIndex() === length - 1) {
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this.currentIndex.set(0);
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} else {
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this.currentIndex.set(this.currentIndex() + 1);
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}
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return this.current();
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}
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prev(): T | null {
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const length = this.list().length;
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if (length === 0) return null;
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if (length === 1) return this.list()[0];
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if (this.currentIndex() === 0) {
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this.currentIndex.set(length - 1);
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} else {
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this.currentIndex.set(this.currentIndex() - 1);
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}
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return this.current();
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}
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add(item: T) {
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this.list.update((list: T[]) => {
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return [...list, item];
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});
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}
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remove(item: T) {
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// Check item is actually in the list, and find its index
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const index = this.list().indexOf(item);
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if (index > -1) {
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// If we deleted an item before the current index pointer, then shift the index back one to maintain current item
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if (index < this.currentIndex()) {
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this.currentIndex.update((index) => index - 1);
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}
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// If we are at the end of the list (and the list won't become empty) shift index back to maintain pointer at end of list
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if (index === this.list().length - 1 && index > 0) {
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this.currentIndex.update((index) => index - 1);
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}
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// Remove the item
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this.list.update((list: T[]) => {
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list.splice(index, 1);
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return [...list];
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});
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}
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}
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}
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